Vice-President’s Address. 307 
Commencement of the Cambrian Period, but not to the 
Commencement of Life upon the Earth. We have long 
known, thanks to the labours of fellow-geologists in 
sritain and in America, that the Lower Cambrian fauna 
contains representatives of all the chief forms of Invertebrate 
Life, and these are in most cases by no means of low 
zoological grade. No one who fully realises the import of 
Evolution as now understood can for a moment doubt that 
this fact points in a manner that is unmistakable to the 
inference that the Beginning of Life upon the Earth must be 
vastly more remote—perhaps as much farther back from 
Cambrian times as they are removed from our own. To me, 
to whom Geology is of interest chiefly as throwing light 
upon the past history of Life upon the Earth, this early 
appearance of highly-organised forms of Invertebrata suggests 
remarks sufficient to double the already considerable length 
of this Address. I must content myself, however, with 
referring the reader to the very thoughtful and suggestive 
address on this aspect of our inquiry which Professor 
Poulton delivered at the 1896 meeting of the British 
Association. 
In regard to the physical and mathematical aspect of this 
question of the Age of the Earth, I, as neither a physicist 
nor a mathematician, can have but little to say. But, so far 
as I can judge, the late Dr Croll’s “Stellar Evolution” 
supplied an answer to one of the main objections to any 
high estimate of the Earth’s Age. Professor Perry, Mr O. 
Fisher, and others have done equally good work in the same 
direction, and have earned the thanks of all geologists for 
their labours in a good cause. 
On my own part, I have only two suggestions to make, 
neither of which, I am told, is new, but of which both seem 
to me to have an important bearing upon the physical 
aspect of the present question. Each shall take the form 
of a query. 
1, Is it certain that the whole of the downward increment 
of heat within the Earth is due to any vestige of the Earth’s 
original heat? If not, why may not part of it be due to the 
conversion of the energy of motion arising from terrestrial 
VOL. XIII. v 
